Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$201.35	13.486%	$228.5041	$228.50	$228.50	$228.50
Purchase #2	$196.96	3.832%	$204.5075	$204.51	$204.50	$204.50
Purchase #3	$108.39	4.567%	$113.3402	$113.34	$113.35	$113.30
Purchase #4	$63.43	11.366%	$70.6395	$70.64	$70.65	$70.60
Purchase #5	$80.31	6.703%	$85.6932	$85.69	$85.70	$85.70
Purchase #6	$239.61	4.532%	$250.4691	$250.47	$250.45	$250.50
Purchase #7	$196.92	11.424%	$219.4161	$219.42	$219.40	$219.40
7 purchase totals =	$1,086.97		$1,172.5697	$1,172.57	$1,172.55	$1,172.50